You are going to need something 365 if you do trials. So no blues. Messanger is great but if you don't have that Three Little Words and Hopscotch pilgrim are close substitutes.

no exotic and no handcannon!!! DO YOU EVEN WANT TO WIN!

Just messing, my primary is usually jewel of osiris. if I had to pick something other than that it would probably have to by hygiea noblesse. or just stick to party crasher or sniping.

A couple of suggestions you could try:

NL Shadow 701x w/full auto for an auto rifle like substitute. Its about as close as you can get to the old Suros pre-nerf. I'd suggest getting Braced Frame/Hand Laid Stock/Smallbore in the 2nd column of perks to increase stability. 3rd perk is your preference. 3rd eye is always great, but I find it slightly less useful in trials because there are less enemies and you are typically calling them out. Also you generally know where engagements are taking place. I would suggest Zen moment for extra stability, or hidden hand to keep on target during rapid fire. Crowd control may be worth looking into, because if I'm correct, it will take you from a 5 shot to a 4 shot with precision damage.

Also in the scout rifle group is the One/One Synesthete from the Vanguard. It's the same RoF/Impact as Mida, without using an exotic slot. You can even build it into a mini Mida. Battlerunner, Lightweight, Third Eye. I'm a stability fan so I went with hand laid stock to give me a near perfect stability. I also rolled full auto because I have a lazy trigger finger.

I'll admit I'm not the best player, so I have learned to play the roll of support class. Staying alive and keeping my Squad leaders revived is my number 1 priority. I can easily do that with a good auto rifle like U4A or a single burst from ALLfate. Then move back and let them snipe the wounded target. Running Crest of Alpha Lupi I can quick revive, make three orbs with my Defender bubble (guaranteed) and an additional three if they damage my bubble enough.